To provide data read/write method and device reducing an area of a semiconductor memory device by using a column decoding line instead of an input/output line connected to a bit line and making possible read/write operation.

The storage data in a cell 11 transmitted to bit lines BL, the inverse of BL are sensed and amplified by a bit line sense amplifier 13, and are selected by a first pass transistor 20 with a block selective low address signal BS to be outputted to the column decoding lines Yi, the inverse of Yi through a second pass transistor 21. The output of the second pass transistor 21 is outputted by a read/write signal outputted from a column decoder 16 to the lines Yi, the inverse of Yi through a multiplexer 17 and a read sense amplifier 15. Thus, the data read/white method and device reducing the area of the semiconductor memory device is obtained.